Real Madrid captain Sergio Ramos (top) celebrates Isco's (below) goal against Atletico Madrid during the Champions League semi-final second leg on Wednesday. Pic/Getty Images

Real Madrid captain Sergio Ramos has warned Juventus striker Gonzalo Higuain not to let their friendship lull him into a false sense of security for next month's Champions League final, and insisted "sparks are going to fly" in Cardiff.